Uterine leiomyomas (fibroids) are the leading indication for hysterectomy in the United States. Despite the morbidity and high medical costs associated with fibroids, there has been little epidemiologic study of this condition in the United States. Uterine leiomyomas are histologically identifiable as benign smooth muscle tumors with varying amounts of associated fibrous tissue. Many women have more than one uterine leiomyoma, but each appears to be clonally distinct. Several specific cytogenetic changes have been identified in tumor tissue, but most show no chromosomal abnormalities. These benign tumors are hormone-dependent. They develop after puberty and regress after menopause. Both estrogen and progesterone are considered important stimulants, or at least permissive factors for tumor growth. To address the research needs in this field we have designed four studies. The first, the NIEHS Uterine Fibroid Study, is a large epidemiologic study of black and white women, aged 35-49, in which the randomly selected participants were screened for fibroids with ultrasound. The second study (Fibroid Growth Study, Shyamal Peddada, PI) is a clinical study of fibroids designed to describe fibroid growth. The third study, Postpartum Uterine Regression, monitored fibroid change with pregnancy and postpartum uterine regression. The fourth study, a prospective study of fibroid incidence and growth. All these studies contributed to our research this year. We continue to analyze data from the NIEHS Uterine Fibroid Study. We found that women low vitamin D status is associated with higher prevalence of fibroids in both black and white women. The data on reproductive tract infections were published with a general review of fibroid epidemiology. Dietary factors are currently being investigated. We are also analyzing data on the relationship between fibroid size and treatment needs. For the Fibroid Growth Study we found that short-term growth spurts were common for fibroids. The growth spurts of individual fibroids in the same uterus did not occur together, indicating that growth regulators are tumor-specific. The stored tumor specimens from the Fibroid Growht Study were examined for genomic loss (and gain) of heterozygosity. We found that small gains were quite common, but major deletions were rare, indicating that tumors do not generally exhibit major genomic instability. For the Postpartum Uterine Regression Study, we found that the shrinkage of fibroids associated with pregnancy is attenuated for miscarriages. In addition, black women do not exhibit as much pregnancy-related tumor shrinkage as white women, and postpartum progesterone use appears to inhibit pregnancy-related tumor shrinkage. We began enrolment in a prospective study of fibroids in November, 2011. Our goal is to enroll 1600 African American women 23-34. We have enrolled 488 to date. The Study of Environment, Lifestyle &Fibroids (SELF) is based in Detroit, Michigan with collaboration from Henry Ford Health Systems. Participants are screened for fibroids with ultrasound at enrollment (detection limit of lesion = 0.5 cm diameter). There will be four subsequent clinic visits at approximately 15-month intervals to monitor fibroids by ultrasound examinations in order to identify onset time. Those found to have fibroids at enrollment (newly detected, not previously clinically diagnosed) as well as those who develop fibroids during the study will be followed in the same manner to assess development of additional new fibroids and to measure fibroid growth. We collect risk factor and symptom data at enrollment and then prospectively for five years. The study is designed to collect a broad spectrum of exposure data including recognized risk factors for fibroids (age of menarche, pregnancy history, alcohol use, body mass index) and potential risk factors for which there has been only suggestive data. Three primmary hypotheses will be tested. (1) Vitamin D deficiency is a risk factor for fibroids, (2) Reproductive tract infections are risk factors for fibroids, and (3) A higher proportion of African ancestry is associated with increased fibroid risk (African ancestry measured by informative SNPs known to have very different frequencies between Europeans and Africans). Enrollment activities include: orientation to study, pre-enrollment self-administered questionnaire, web-based questionnaire, food-frequency questionnaire, computer-assisted telephone interview, clinic visit with ultrasound. measure of blood pressure, weight, height, skin reflectance, specimen collection (blood, urine, vaginal swabs), menstrual cycle diary to prospectively record at least one menstrual cycle and bleeding pattern, and an early life questionnaire that the participant administers to her mother (if available).